The white-nose syndrome fungus transcriptome

Pseudogymnoascus destructans is the causal agent of bat white-nose syndrome (WNS), which is devastating some North American bat populations. Identifying P. destructans virulence factors directly supports bat conservation efforts by providing an assembly of candidate genes to target with potential treatments. In vitro studies allow more controlled transcriptomic analyses and reduce the impact of WNS research on wild bats, but this approach requires that P. destructans responds similarly when growing in culture under different conditions, or on a bat. To test this assumption, we cultured three isolates of P. destructans on potato dextrose agar and Sabouraud dextrose agar at two separate incubation temperatures (4°C and 15°C), and conducted RNA-sequencing to determine transcript levels in each sample. We conducted differential gene expression analyses to compare the transcriptome of P. destructans under these different in vitro conditions, and compared our in vitro results to previous RNA-sequencing datasets generated from P. destructans growing on the wings of Myotis lucifugus. Growth media and incubation temperature had a significant effect on transcript levels, and P. destructans transcript expression varied between growth in culture or in a pathogenic context (on WNS-affected bat tissue). However, we found that surprisingly few proteins with sequence similarity to characterized virulence factors were up-regulated in a pathogenic context. These findings support the utility of in vitro research for understanding WNS provided that environmental conditions are considered. Overall, our results support the hypothesis that P. destructans acts as an opportunistic or incidental pathogen, rather than a pathogen that exhibits specific pathogenic responses during infection.